Oscillation generator



K. POSTH UM U S OSCILLATION GENERATOR Dec. 28, 1937.

Filed July 25, 1934 A ZNVENTOR KLAAS POSTHUM US ATTORNEY Patented Dec. 28, 1937 PATENT OFFICE OSCILLATION GENERATOR Klaas Posthumus, Eindhoven, Netherlands, 215,- signor to Radio Corporation of America, a corporation of Delaware Application July 25, 1934, Serial No. 736,859

In the Netherlands September 6, 1933 2 Claims.

This invention relates to a novel and suitable device for generating electric oscillations of extremely high frequency. I

It-is well known in the art to use thermionic generators of the kind wherein oscillations are produced under the action of a magnetic field in order to generate high frequency oscillations.

There are two such groups of generators, the first comprising those having a single cylindrical anode surrounding a linear cathode. With this first type of generator, there are produced electric oscillations having a frequency whose time of oscillation is of the same order of magnitude as the time of circulation of the electrons within the tube. These oscillations correspond to the oscillations generated in a triode wherein the grid has a higher positive voltage than the anode relative to the cathode. The second group comprises those generators in which two or more anodes are symmetrically arranged with respect toan incandescent cathode. With this group a negative resistance occurs when a potential difference is setup between two opposite anodes. If an oscillatory circuit is provided between the opposite anodes, oscillations will be produced therein due to the negative resistance, the frequency of said oscillations depending on the natural frequency of said circuit.

Generators of the last mentioned type have the disadvantage of not being able to produce oscillations below a certain wave length, since with this wave length the inertia of the electrons prevents the production of oscillations.

The present invention has for its object to pro vide an improved generator of the last mentioned type so that there may be produced oscillations having a higher frequency than has hitherto been possible.

7 According to the invention this object is achieved by using a generator comprising at least two pairs of anodes in which the anodes are alternately electrically connected together.

being symmetrically arranged with respect to an incandescent cathode 6 which is normal to the plane of drawing. The field winding, whichis fed by rectified alternating current or directcurrent and is arranged in such a manner that the lines of force extend substantially parallel to the cathode, is represented by the dotted line it in the drawing. Between the anodes 2 and 51 there is provided an oscillatory circuit consisting of an inductance H and a condenser I0. Let it be assumed that the generator is oscillating and that at a given moment the voltage set up at the anode 2 increases, whereas the voltage set up at the anode 4 decreases, then the electrons will substantially be attracted by the anode 2. However, by adjusting the intensity of the magnetic field to the right value, the electrons take a curved path as shown by the closely dotted lines within the envelope. Due to this the electrons attracted by the anode 2 will reach the anode 4, thus contributing to the decrease of the anode voltage of the anode 4. This continues till after a half cycle of the oscillations in the circuit lill I, the polarity of the anodes 2 and 4 reverses, and the voltage set up at the anode 4 increases Whereas that set up at the anode 2 decreases. The electrons will now take such a path that they impinge on the anode 2 and tend to promote the decrease of the voltage of the anode 2.

This arrangement has the drawback that if the natural frequency of the oscillatory circuit Ill-H is high, the electrons attracted by the anode 2 (when the voltage set up at the anode 2 increases) strike the anode 4 only if the voltage of this anode increases too, which is due to the fact that the time during which the electrons pass from the cathode to the anode, is longer than half the time of oscillation of the oscillations produced in the circuit Ill-II.

It will be appreciated that with the natural frequencies of the external oscillatory circuit, it half the time of oscillation is longer than the time during which the electrons pass from the cathode to the anode, then practically no oscillations are produced.

However, by means of the arrangement according to the invention, of which an embodiment is represented in Fig. 2, appreciably larger frequencies can be generated than with the aid of the arrangement shown in Fig. 1. The arrangement according to the invention comprises at least'four anodes alternate ones of which are electrically connected together, which connection may be established either outside or inside the tube. Preferably, this connection is established inside the tube. I also provide a system 9 which is tuned to the generated frequency and preferably consists of an evenly distributed inductance and a capacity. One leg of this sys tem connects the anodes 2 and 4 with one terminal of the tank circuit Hl-l l. The other leg similarly connects the anodes 3 and 5 with the opposite terminal of the tank circuit Ifl-l I.

Assuming now the generator to be oscillating and the voltage of the pair of anodes 2, 4 to be increasing, whereas that of the pair of anodes 3, 5 decreases, then the electrons attracted by the anodes with the increasing voltage will move along the paths indicated in dotted lines to the anodes 3, 5. The path to be taken by the electrons during half the time of oscillation of the oscillations in the circuit l0--ll is much shorter than in the known arrangements.

The oscillations produced by the generator may be transmitted through an antenna 12, if desired, after having been modulated in a known manner in amplitude or in frequency.

What is claimed is:

1. An oscillation generator comprising an electron tube having an electron emissive cathode, a plurality of anode sections surrounding said cathode all within an evacuated envelope, and means for producing a magnetic field surrounding said electrodes, comprising two pairs of oppositely disposed anode segments in the form of arcuate segments on a circle, opposite segments of each pair being connected together, in combination with a tunable oscillatory circuit comprising an inductance and a condenser in parallel, a connection from one terminal of said oscillatory circuit to one pair of segments, and a connection from the other terminal of said oscillatory circuit to the other pair of segments, a connection from a point intermediate the ends of said inductance including a source of potential to said cathode, and a mi lization circuit coupled to said inductance.

2. An oscillation generator comprising an evacuated electron discharge tube of the magnetron type having a linear cathode and at least four cylindrically segmented anode members co-axially disposed with respect to the cathode and surrounding the same, in combination with circuit arrangements including a tank circuit one terminal of which is connected in parallel to alternate ones of said anode segments and the other terminal of which is connected in parallel to intervening anode segments.

KLAAS POSTHUMUS. 

